doug , i dont know how much rubber comes off of the washers but i had a tiny pieces of rubber issue that was caused by the black rubber "turtleneck" , the rain/ fuel overflow catcher that is around the fuel filler neck . they place it and a cork gasket between the filler neck and the tank . i dont know if it is dry rot or what , however tiny pieces eventually flake off into the tank and clog everything from the tank outlet forward . i found a bill under the seat to the previous owner, from a shop that cleaned out the tank and lines , rebuilt the carbs , and charged an arm and a leg to do it . later i saw that they had grounded the battery to the carb . not a very good idea . the clogging cropped up again for me after a spirited ride through the ilion gorge on rt 51 , i replaced the fuel filters and discovered that one of them was literally resting on the exhaust header. another not very good idea . then it was on to an electric fuel pump . another tank cleaning and this time removed the rubber overflow thingamajig and replaced it around the fillerneck and not under it as a gasket . troublefree since then , so far . good luck sorting out the problem . hope this helps you some .